The story of Fahrenheit 451 takes place in a dystopian future in which people have limited freedom of speech and education and curiosity has become a criminal act.
Given the fascist world in which they live, the reader could easily assume that their freedoms had been taken away by force. It is later learned, however, that the government never had to take anything from the people because they willing gave up their freedoms in favor of convenience, security, and contentment. Captain Beatty explains to Guy that people had grown tired of the competition, complexity, and frequent challenges that accompany life, which is why they slowly conceded their autonomy to modern conveniences like machines and television and became content to let the government make decisions for them, believing that they would do what's best.
As is often demonstrated throughout the book, the government is able to maintain this control of the people by prohibiting things like reading books or gathering for intellectual discussions. Those who challenge or violate these rules are punished harshly, which serves as an example to anyone who might consider defying the law.
Bradbury's intent, among other things, was to show how this type of complacency and authoritarianism is not only anti-intellectual but also dangerous. While everyone is attempting to be happy and avoid the negativity and challenges of life, they all fail to notice how serious the war has become, which eventually destroys them. This aspect of the story is brilliantly demonstrated by the fact that the war is rarely mentioned throughout the story, until the bombing begins and it is too late for anyone to save themselves.